The invention relates generally to molded window gaskets and to the reaction injection molding of such articles from a multi-constituent material in a mold cavity. More particularly, the invention relates to such gaskets for automotive applications and to equipment and methods of reaction injection molding of such articles, wherein the elastomeric window gaskets are integrally molded onto a window panel of glass or other transparent material.
It has been known in the past to fabricate articles such as modular window gaskets for vehicular installations from materials such as polyvinylchloride (PVC) using conventional compression or injection molding techniques. Some of such window gaskets have been injection molded directly onto the window panel, which is made of glass or other substantially transparent material. The window and gasket assemblies have then been installed in a vehicle or other window frame with adhesives and/or with integrally molded fastener protrusions, as disclosed, for example, in U.S. Pat. Nos. 4,072,340 and 4,139,234. It has been found, however, that window panel breakage has been unacceptably high in such prior processes because of the high pressures required in the injection molding processes and because of the hardness and rigidity of the mold structures involved. Additionally, because of the types of materials previously used in molding the gaskets, such as rubber or polyvinylchloride (PVC), it has been found that proper adhesion of such gaskets to metal body panels and to glass window panels has been difficult to attain, thereby resulting in water leaks, wind noise, and other related problems, as well as requiring the use of mechanical fasteners to secure the assemblies to the body panels.
In accordance with the present invention, improved apparatuses and methods of reaction injection molding articles such as vehicular window gaskets are provided in order to overcome the above-discussed disadvantages. Such methods and apparatus allow window gaskets to be reaction injection molded from multi-constituent liquid materials, such as urethane, for example, and to be molded at relatively low pressures directly onto the glass or other transparent window panels. The gasket and window panel assemblies can then be mounted directly into a window opening in a body panel and secured thereto with adhesives without the need for mechanical fastener devices, thereby simplifying the installation process and making it better suited for robotic or other automated equipment. All or a portion of the gasket can also be coated with a pigment decorative material in the mold cavity if desired.
The gaskets according to the present invention may also be fabricated with a lower cross-sectional profile, thereby providing for a smooth aerodynamically advantageous fit between the window assembly and the body panel. Such lower profile also requires less offset or other forming of the body panel area surrounding the window opening, thus simplifying the body panel fabrication and increasing the design flexibility for such body panels. Also, because the gasket and window assembly is preferably bonded and secured to the body panel substantially continuously around the window opening periphery, the localized stress concentrations caused by spaced, discrete mechanical fasteners are substantially avoided and the bonding and securing forces are more evenly distributed. This allows the window panel to effectively contribute to the structural integrity of the installation, and also to allow for a reduction in window panel thickness and weight.
In a preferred embodiment of the present invention, an aftermixer apparatus for use in a reaction injection molding system includes a mixing body having at least one common inlet passageway for receiving a multi-constituent material in a pressurized flowable state. The apparatus includes a number of mixing passageways adapted to receive the material from the common inlet passageway and separate it into a corresponding number of material flow streams. A common mixing cavity in fluid communication with the mixing passageways reunites the separated flow streams and conveys the material into a gating device for introduction into the mold cavity. Adjustment means is provided for selectively altering the size of the common mixing cavity and the size of its inlets in order to selectively alter the back-pressure exerted on the material flowing therethrough. Such adjustment feature allows for the optimization of the back-pressure and thus the intermixing of the constituents of the material for a given flow rate and inlet pressure thereof. Preferably, the mixing passageways each extend along a generally sepentine path including at least one bight portion adapted to cause the material flowing therethrough to substantially reverse its direction of flow in order to increase turbulence and enhance the mixing of the material constituents.
At least a portion of the preferred mold cavity of the reaction injection molding system includes one or more elongated elastomeric members positioned generally adjacent the peripheral edge of the mold cavity for supportingly engaging the mold members and the window panel. The flexible elongated elastomeric members are preferably seated in grooves in one or the other of the mold members and are further adapted to substantially minimize or prevent flashing of the gasket material out of the mold cavity and also serve to accommodate variations in the shape of the window panels.
Additional objects, advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.